1. Field of the Invention
The present invention relates to the manufacture of semiconductor devices. More particularly, the present invention relates to the integration of high speed waveguide structures into standard complementary metal oxide semiconductor (CMOS) chips.
2. Description of the Related Art
Today""s semiconductor devices are continually being pushed to meet stricter demands. As devices using this technology inundate the marketplace, consumers place higher demands on the devices. These demands include smaller, more compact devices with greater functionality.
In the search for higher performing circuitry, designers of CMOS circuitry have been looking to other technologies. Such technologies include, for example, radio frequency (RF) technologies, microwave frequency technologies, and optical frequency technologies. A problem, however, is that such technologies are not capable of being integrated using the same process operations implemented in standard CMOS design. As a result, when the need arises for faster performing circuitry, integrated circuit designers are forced to separately design and manufacture separate chips and then integrate them using printed circuit boards (PCBs).
As is well known, separate design and manufacture is required due to the differences in fabrication. That is, standard fabrication operations implemented in making CMOS devices an not readily be applied to the making of RF circuits, microwave circuits, or optical circuits. For example, many RF circuits require that conductive lines be formed as co-axial structures having an inner conductor and an outer shield. Some microwave circuits are made using microstrip technology and steel waveguides with or without filling dielectric materials. Optical devices are also often fabricated using multiple dielectric layers and specially arranged conductors.
Once both the CMOS chip and either an RF device, microwave device, or optical device is ready for integration, substantial work must be performed to ensure that proper communication is made between signals of the two technologies. This testing often requires substantial investment in time and many times produces a device that fails to meet strict performance requirements. This failure in performance is primarily due to the separate manufacturing processes and signal or power losses experienced when the separate chips are interfaced. In addition, separate manufacture and integration also has the downside of increasing engineering costs and thus final product cost.
In view of the foregoing, there is a need for a semiconductor device that can integrate both standard CMOS circuitry along with other non-CMOS high speed circuitry. There is also a need for methods for making the semiconductor device using standard CMOS fabrication processing.
Broadly speaking, the present invention fills these needs by providing semiconductor devices that incorporate non-CMOS high speed circuit structures along with standard CMOS circuitry. It should be appreciated that the present invention can be implemented in numerous ways, including as a process, an apparatus, a system, a device or a method. Several inventive embodiments of the present invention are described below.
In one embodiment, a method for making a waveguide structure implementing CMOS fabrication processes is disclosed. The method includes providing a substrate having a plurality of active devices fabricated therein and an overlying oxide layer. A contact hole is defined through the oxide layer to define a path down to the substrate. The method then moves to where a first metallization coating is deposited over the oxide layer and in the contact hole. The first metallization coating is removed at a base of the contact hole to define the path down to the substrate and the contact hole is filled with a contact hole dielectric material. A waveguide dielectric is then formed over the first metallization coating and in contact with the contact hole dielectric material. A second metallization coating over the waveguide dielectric is then formed. The method then moves to patterning the second metallization coating, the waveguide dielectric, and the first metallization coating. The patterning is configured to leave a partial waveguide structure that has the contact hole dielectric material in contact with the waveguide dielectric. A third metallization coating is formed over the partial waveguide structure. The third metallization is configured to define metallization spacers that connect the first metallization coating and the second metallization coating and enclose the waveguide dielectric to define the waveguide structure.
In another embodiment, a method of making a waveguide for communicating optical signals is disclosed. The method includes forming a contact through a dielectric layer down to a substrate and coating sidewalls of the contact with a first metallization coating. The contact is then filled with a dielectric material. A partial waveguide structure is formed over the first metallization coating and the dielectric material of the contact. The partial waveguide structure is defined by a waveguide dielectric structure and a second metallization coating that is defined over the waveguide dielectric structure. A third metallization coating is then formed to define spacers along sides of the partial waveguide structure, the first metallization coating, the second metallization coating. The third metallization coating is configured to complete the waveguide structure that is filled with the waveguide dielectric structure. Optical signals can then be propagated through the waveguide structure and interfaced with other CMOS digital circuitry.
In yet another embodiment, a waveguide structure integrated into a semiconductor device and fabricated using standard CMOS processing is disclosed. The waveguide structure includes: (a) a substrate having a light emitting diode fabricated therein; (b) a conductive material coated and dielectric filled contact being in communication with the light emitting diode of the substrate and (c) a conductive material coated dielectric line being in dielectric contact with the conductive material coated and dielectric filled contact, the conductive material coated dielectric line defining the waveguide structure.
The many advantages of the present invention should be recognized. A semiconductor application can now integrate waveguide structures and standard CMOS features on a single chip. As such, designers are no longer required to design and fabricate separate chips having waveguide structures and CMOS chips to make a desired integrated circuit application. Other aspects and advantages of the invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.